Osteotomies about the knee have been an important component of the surgical treatment in the management of knee osteoarthritis. The ultimate goal of knee osteotomies has been to relieve pain symptoms, slow disease progression and postpone total knee arthroplasty in younger patients by transferring weight bearing load to the relatively unaffected portions of the knee.
The most commonly performed knee osteotomy has been the proximal tibial osteotomy or “high tibial” osteotomy. The first reported tibial osteotomy was in 1958. Knee osteotomy principles and techniques continued to evolve through the 1960s and 1970s. Today, however, other than at a minority of leading orthopedic centers, proximal tibial osteotomies are generally regarded critically by the general populace of orthopedic surgeons. The overall community holds the opinion that, first and foremost, the surgical technique of osteotomy is challenging and cumbersome, requiring much practice in the “art” in order to effectively perform and reproduce the osteotomy procedure.
More particularly, current techniques generally require the passage of hand-directed guidewires and hand-guided bone resecting tools while requiring continual use of fluoroscopy throughout the procedure. In such a procedure, the failure to properly execute the required precision can lead to a lack of, or postoperative loss of, correction and complications such as delayed union or nonunion, unintended changes to the slope of the tibial plateau, intraarticular fractures, and neurovascular problems. All of these issues pose a direct risk to a successful surgical outcome. In addition, the postoperative rehabilitation period using current techniques may require a conservatively long duration so as to protect the osteotomy from potential nonunion during the long healing period. Also, currently practiced procedures often require a second surgery to remove fixation hardware.
The reported long-term surgical outcomes of high tibial osteotomy procedures vary considerably. Published research of these procedures demonstrates that the relief of pain and restoration of function is generally achieved in approximately 80% to 90% of patients at five years, and 50% to 65% of patients at ten years.
The methods and principles of surgically performing an osteotomy have slowly developed over time. The two common osteotomy methods are: (i) the lateral closing wedge method; and (ii) the medial opening wedge method (with either an internal fixation device or an external fixation device). Within these two general categories of surgical methods, there are varying nuances to the surgical techniques purported by individual orthopedic surgeons. For example, in discussions with individual surgeons, it is common to hear “this is how I do it” inasmuch as no “gold standard” surgical technique has emerged to date.
The lateral closing wedge method has been the traditional method for osteotomy surgery. This is the most common osteotomy for medial compartment osteoarthritis. Correction of alignment is typically achieved by first removing a laterally-based, angled wedge of bone, and then closing the resultant opening.
The medial opening wedge method with internal fixation has been gaining in popularity in recent years. Correction of alignment is typically achieved by first making a single transverse bone cut into the medial sagittal plane of the knee, and then manually opening the cut under fluoroscopy with a series of osteotomes, or pre-sized wedge osteotomes. This technique generally provides the surgeon with the intraoperative ability to more easily achieve the required correction angle. The wedge opening is then fixated at a given height with a small fixation plate and bone screws that support the opening of the wedge osteotomy. The opened bony void is then filled with bone graft material.
The medial opening wedge method with an external fixation device is most often used when a large correction is needed in order to achieve proper alignment. Correction of alignment is achieved by first making a single bone cut into the medial sagittal plane of the knee. Next, an external fixation device is applied and then regularly adjusted, in small increments, usually on a daily basis, so as to slowly open the wedge to a desired correction angle. The progress of this surgical technique is usually confirmed with weekly radiographs.
The opening wedge technique has been advocated as a faster, simpler surgical procedure that can be more easily learned while providing a better method for achieving the desired corrective angle with minimal risks to surrounding neurovascular structures. However, the various opening wedge surgical techniques, as currently practiced, allow a wide window for the introduction of surgical error.
All of these opening wedge osteotomy techniques, as currently practiced, require the hand-guided placement of guide pins to define the anterior-to-posterior tibial slope, sometimes referred to as the AP tibial slope, and require the use of hand-held and hand-guided osteotomes, which are all used under fluoroscopy. The use of frequent fluoroscopic pictures is critical to determine the work performed to that point in the procedure and the required adjustments still to be made in the remainder of the procedure. Errors by the surgeon in defining the AP tibial slope can result in an inappropriately-placed osteotomy with unintended changes to the tibial slope, which in turn may affect knee stability. Errors in the use of hand-driven osteotomes or hand-guided saw blades in creating the bone cut can lead to tibial slope changes, migration of the osteotomy into the joint, and/or injury to neurovasculature and soft tissue structures.
Recent evolutionary developments in osteotomies have focused on two general components. One of these includes improved wedge-shaped osteotomes which are used to form or open the bony wedge osteotomy. The other includes low profile internal fixation plates used during the nonweight-bearing rehabilitation phase to rigidly maintain the wedge opening, and used during the weight-bearing rehabilitation phase to add support to the entire osteotomy site. While significant, these advances do not address important issues including, but not limited to, the reduction of the surgical learning curve to make the procedures more reproducible, the improvement of the surgical precision of osteotomy procedures, the reduction in the use of fluoroscopy, and the fact that internal fixation devices used in an open wedge osteotomy effectively stress-shield the osteotomy or fracture site. Such stress-shielding is often a factor in complications involving nonunion and loss of correction.
Today, the orthopedic surgeon's requirements are demanding prior to the adoption of a new surgical procedure. The actual demands include a predictive knee osteotomy procedure with accuracy in determining the correction angle before surgery, and precision in carrying out the surgical technique with reproducible results. The ultimate surgical outcome depends upon the ability of the surgeon to precisely execute the corrective angle and to ensure that the correction remains long lasting.